Fluid heat exchange apparatus



J1me 10, 1941. N M 2,245,209

FLUID HEAT EXCHANGE APPARATUS Filed Jan. 31, 1936 4 Sheets-Sheet l 1/4110 P3 86 170 M INVENTOR.

B Bdrm H-NMayo June 10, 1941. MAYO 2,245,209

FLUID HEAT EXCHANGE APPARATUS Filed Jan. 51, 1936 4 Sheets-Sheet 2 Fig 2WM F1 :3

INVENTOR.

Dalia H. N Mayo AT RNEY.

June 10, 1941. D. H. N. MAYO 2,245,209

FLUID HEAT EXCHANGE APPARATUS Filed Jan. 31, 1956 4 Sheets-Sheet 3Fig.5-

= I INVENTOR- Q 6 9) Dana HIV Mayo ATTORNEY.

June 10, 1941. N, MAYO FLUID HEAT EXCHANGE APPARATUS Filed Jan. 31, 19564 Sheets-Sheet 4 INVENTOR. Dana HM Mayo ATTORNEY.

Patented June 10, 941

FLUID HEAT EXCHANGE APPARATUS Dana H. N. Mayo, Ridgewood, N. J.,assignor to The Babcock & Wilcox Company, Newark, N. J., a corporationof New Jersey Application January 31, 1936, Serial No. 61,704

21 Claims.

This invention is concerned with fluid heat exchange apparatus and ishere exemplified in a water tube steam boiler associated with asuperheater.

It is a matter of prime importance in the operation of modern powerplants that superheat temperatures be kept within a limited range. Thisis especially true when superheats in excess of 800 F. exist. Excessivevariations above such temperatures not only involve uneconomicalutilization of fuels but also endanger turbines or other prime moversutilizing the superheated vapor. It is an object of this invention toprovide a vapor generator so associated with a superheater that suchexcessive superheat temperatures may be prevented and a predeterminedsuperheat maintained.

Among its other objects the invention seeks to provide an efiectivesuperheater boiler having fluid cooled walls so constructed thatmulti-loop superheater coils may be removed or replaced by moving themthrough one of those walls and without disconnecting any of the tubeswhich cool the walls.

Another object of the invention is to provide a superheater boiler inwhich high capacity and a high degree of superheat control may beattained even though a pulverized coal fired furnace be utilized. Hieinvention comprehends a double slag screen preventing excessive slaggingof the superheater tubes.

Other objects will appear as the accompanying description proceeds.

The invention will be described with reference to the accompanyingdrawings, in which:

Fig. 1 is a view in the nature of a vertical section ,through a steamgenerating installation embodying the invention.

Fig. 2 is a view in the nature of a side elevation showing a part of oneside of the installation indicated in Fig. 1. It is taken from theposition indicated at 2-2 oi Fig. 1 and looking in the direction of thearrows.

Fig. 3 is a view in the nature of a vertical section taken on the line3-3 of Fig. 1 and showing a part of the installation.

Fig. 4 is a detail View showing the manner in which the intermediate gaspass baflle tubes are arranged with reference to the steam and waterdrum.

Fig. 5 is an upright view taken on the line 55 of Fig. 4 and showingsome of the parts in vertical section.

Fig. 6 is a detail horizontal section showing the arrangement of walltubes at those parts of the furnace walls which are provided withopenings through which the superheater and economizer tubes may beremoved and replaced. .This view is taken on the line 6-6 of Fig. 1.

Fig. 7 is a vertical section of a modified form of the Fig. 1 boiler.

Fig. 8 is a horizontal section of a stud tube wall including the walltubes 68 and 10 of Fig. 5.

Fig. 9 is a diagrammatic detail view in the nature of a vertical sectionillustrating the manner in which the coils of the superheater or theeconomizer may, be supported by the wall'tubes at opposite sides of thegas passes 28 and 30.

Fig. 1 of the drawings discloses a furnace in which there are twocombustion chambers l0 and I 2. They are separated by the fluid cooledtubes it and i6, the upper. parts or which diverge upwardly and arespaced vertically so as to form the slag screens l8 and 20. The tubes ofthe slag screen I 8 extend across the gas outlet of the combustionchamber I0 and the tubes of the slag screen 20 bear a similar relationto the combustion chamber l2.

The furnace gases from the combustion chambers i0 and i2 pass across thetubes of the slag screens I8 and 20 into a secondary combustion chamber22, and thereafter contact with the fluid cooled tubes of the slagscreens 24 and 26, and are divided so as to proceed in parallel throughtwo gas passes 28 and 30.

In the gas pass 30 the gases first contact with the superheaters 32 and34, and then pass over the tubes of the first economizer section 36.Thence they pass to the flue 38 where the flow is controlled by aregulator 40.

In the gas pass 28 the gases contact with the second and thirdeconomizers 42 and 44, and afterwards pass to the flue 46 where the gasflow is controlled by the regulator 48. Beyond the regulators 40 and 48the gases pass through outlets 50 and 52 to an air heater which may belocated at Water delivered under pressure to the economizers passesthrough them and the header 56 and the tubes 58 to a steam and waterdrum which is in circulatory connection with the slag screen tubes andthe wall tubes to be described. Steam generated in these tubes passes tothe drum, preferably above its water level, and downcomer connectionscomplete the circulatory connection between the drum and the steamgenerating tubes.

A substantial part of the total steam is generated in the tubes of theslag, screens '24 and 26. They converge upwardly from the lateral waterdrums 62 and 64 to an intermediate submerged drum 66 which may beprotected against overheating by refractory disposed between it and theoncoming furnace gases.

Steam, or a mixture of steam and water is delivered from the submergeddrum 66 to the steam and water drum 60 through the battle tubes 68 and10 which preferably communicate with the drum 60 slightly above itswater level. Between the gas passes 28 and 30 the tubes 68 and 10 may bein row alignment and the spaces between the tubes closed by refractorymaterial. This may be installed as a plastic around metallic studs whichare in good heat exchange relation with the tubes.

The water drums 62 and 64 communicate with the water space of the drum60 through wall tubes I2 and -I4, the latter being preferably arrangedin row formation so as to delineate the gas pass wall 16 which is sorelated to the similar opposite wall I8 as to form a total gas passagewhich tapers upwardly as shown.

The downcomer connections supplying the tubes I4 and I6 with waterinclude the header 80, the hopper tubes 82 and 84 and the headers 86 and88. The latter communicate with large diameter downcomers 90 and 92which are connected at their upper ends to headers 94 and 86. The waterspace of the drum 60 is connected to the header 94 by a plurality oftubes 88 and, similarly arranged tubes I establish communication betweenthe header 96 and the drum 60.

Steam generated in the tubes I4 and I6 and the slag screens I8 and 20passes to the headers I02 and I04 and thence through upcomers I06 andI08 directly to the water space of the drum 60.

The walls of the combustion chambers I0 and I2 opposite the dividingtubes I4 and I6 include wall tubes IIII bent at their lower ends to formhopper bottoms for the combustion chambers and connected to upper andlower headers H2 and H4. The latter preferably communicate with thewater space of the drum 60 through downcomer tubes II8, the drums 62 and64, and the tubes I2 and 14.

From the upper headers H2, wall tubes I20 extend in row formation infront of the pulverized coal burners I22 and thence upwardly past theheaders I02 and I04 to positions wherein they are connected to theuppermost water wall headers I24. The latter deliver steam through theuptake tubes I28 directly to the steam space Y of the drum 60.

In the installation indicated in Fig. 1, steam passes from the top ofthe steam space of the drum 60 through tubes I30 to the inlet header I32of the superheater 84. From this superheater it passes to the header I34and then through to tubes of the superheater I32 to an outlet header I36from which it may be directed to a point of use.

When pulverized coal is used as a fuel the burners I 22 are suppliedwith fuel from the bunkers I40 by means of the feeders I42. The latterdeliver the pulverized fuel to the outlets of the ducts I44 where it isentrained in the primary air passing from the ducts I46 into the burnertubes I48. Movement of airthrough the ducts I46 is caused by the fans I56 which may be driven by motors I52. The burners I22 are preferablydown-shot burners supplied with secondary air through the boxes I54. Theburners preferably direct the flame in a U-shaped course, firstdownwardly towards the hoppers I56 and I58 and then upwardly alongsidethe wall tubes I4 and I 6.

Besides the independently operable sets of burners I22, the separatecombustion chambers III and I2 are shown as supplied with independentlyoperable gas burners I60 and I62. They are indicated as situated alongthe upright sides of the furnace. and connected with the gas means I64and I66.

The burners are arranged in rows extending from front to back along eachof two opposite side walls. Consequently, the furnace gases rising tothe banks of tubes which extend from front to back have the sametemperature of approach to each tube equally from front to back,especially the banks of superheater tubes. Also, the Fig. 1 boiler has,beyond the furnace, two gas passes into either of which the gases fromall of the burners may be directed. The superheater being inone of thesepasses, all of the superheater tubes from front to back receive gases ofthe same temperature, but the amount of gases is controllable toregulate superheat. Such regulation is also effected by varying thetemperature of the gas stream rising on the side of one gas pass.

With the illustrative apparatus, superheat may be closely controlled,and a substantially constant superheat maintained while the boiler loadvaries over'a wide range.

The control of the superheat is exercised through the variation oftemperature and quantity of the gases passing over the superheater, thegases leaving the furnace being substantially divided into two streams,one of which sweeps the superheater and the other sweeps boiler heatingsurface carrying fluid at or below the saturation temperature. The setsof burners for the combustion chambers I0 and I2 may be independentlyoperated to accomplish a part of these results, and the arrangement ofthe slag screens I8 and 20 and the wall tubes I4 and I6 is such that thetwo streams of gases coming from the different combustion chambers neverthoroughly mix. On the contrary, they will remain largely separated. Thetotal efllux of gases from the furnace may be considered as stratifledor laminated so as to constitute three streams flowing in parallel. Themiddle stream will be more or less of a mixture of the other two and theother two will consist of the products of the independently operablesets of burners for the different combustion chambers. The stream on thesuperheater side of the furnace can be made hotter or colder than theother stream by the control of these burners, to effect superheatcontrol.

In addition to the superheat control caused by the independent operationof the different sets of burners the proportion of the total gasespassing over the superheaters 82 and 34 may be controlled by theoperation of the regulators 40 and 48. The boiler thus has a dualcontrol of superheat. The control devices may be operated cooperatively,the two sets of burners varying the gas exit temperature on thesuperheater side with reference to that on the other side of the furnacewhile the regulators 40 and 48 vary the quantity of hot gases permittedto sweep the superheater.

The banks of tubes I8, 20, 24 and 28 cooperate to form a composite slagscreen in which there are two pairs of oppositely diverging banks oftubes. The banks of tubes constituting the lower part of the slag screenconverge downwardly toward a central position in the furnace while thebanks of tubes 24 and 26 constituting the upper part of the slag screenconverge upwardly toward a position somewhat toward the economizer sideof the upper part of the installation. With this arrangement there is atendency for the furnace gases to be first turned convergently towardthe opposite sides of the furnace, and thereafter be oppositely turnedto a central position, this multiplicity of turns promoting effectivedeposition of solid particles from the gases. This arrangement of thecomponent parts of the composite slag screen also provides a. centralpath of gas travel which is longer than the paths at either sidethereof, and, as shown, it provides an undivided space above the furnacedividing wall consisting of the tubes I4 and I6. In this space,combustion may be carried'further toward completion, and rapidabsorption of gas radiated heat is promoted.

Each of the hoppers I56 and I58 is shown as provided with ash removalmeans I and, preferably adjacent the hopper bottoms, some of the walltubes I12, connected to the headers I14 and I15, are bent out of theirrow formation so as to provide elongated openings I16 and I18 throughwhich the coils of a superheater or an economizer .may be removed andreplaced.

The specific arrangement of the tubes to provide the opening I16 isillustrated in Fig. 6. Below the opening I 16 the tube I12 is in rowalignment with the adjacent wall tubes. Above this position it is bentoutwardly to the position indicated at I12", and then alongside theopening I16 it is bent laterally. A reversed arrangement exists abovethe opening I16, and the opening may be normally closed by a cover plateI96. The latter may be latched, or spring pressed to a closed position.

Figs. 4 and 5 illustrate a construction in which the tube sections 68and 16 are pendently supported from the drum 66. As shown, short tubesections I92, closed at their lower ends, are in communication with thewater space of the drum 66, and expanded into the drum, or otherwisesecured thereto. Fig. 5 illustrates each of these sections as havinglugs I94 and I96 welded to its lower end, and extending beyond the lowerend of the tube section. A similar upwardly extending lug I98 is weldedto the tube 16 and attached to the lug I96 by any suitable means such asthe bolt 26!]. The opposite tubes 68 have similar lugs 204 weldedthereto and secured to the lugs I94 in a similar manner.

The boiler indicated in Fig. '7 of the drawings is, in many respectssimilar to that shown in Fig, 1. The primary combustion chambers I0 andI2 are the same, and the arrangement of the auxiliary heating surfaceelements in two parallel gas passes above the steam generating sectionis similar, but the latter includes upright sectional headers. Thedowntake headers 2H) and 2I2 are connected with the water space of thedrum 60 by the wall tubes of the walls 16 and 18, and the uptake headers2I4 and 2H5, converging at their upper ends, communicate with the steamspace of the drum 60 through the partition wall tubes 68, 69, and 10.These tubes pass directly through the drum wall and extend up in thedrum to a position above the water level, as shown.

At the entrance of the gas pass 36 the tubes of the bank 220 connect theheaders 2III and 2I6, and a similar bank of tubes 222 extends across theentrance of the gas pass 28 where they connect the headers 2I2 and 2I4.

Cross headers 224 and 226 are connected to the headers 2H] and 2I2 bythe nipples 228 and 230 and circulation through the boiler slag screentubes 232 and 234 is thus provided. The latter are connected at theirupper ends to the cross headers 236 and 236, whichin turncommunicatewith the sectional headers 2 and M6 at the lower ends of thelatter. Movement of the furnace gases into the space between thesesectional headers is prevented by a baflle 240 which prefer 1. In awater tube steam boiler, a furnace fired,

by two sets of burners positioned on opposite sides thereof and dividedbetween said sets by a row of water tubes, walls forming a plurality ofgas passes arranged in parallel and receiving the furnace gases, asuperheater in one of said passes at one side of the boiler, and aneconomizer in another pass, one of said sets of burners being disposedat the superheater side of the furnace and the other set at theeconomizer side.

2. In a vapor generator, a furnace from which two gas passes lead inparallel, means forming auxiliary fluid heating surface other than vaporgenerating surface in one of the passes, two sets of burners on oppositesides of the furnace with one set being on the auxiliary heating side ofthe furnace, a row of fluid cooled tubes positioned between said burnersets so as to divide the furnace, means including tubes defining acombustion chamber common to both gas passes, and vapor generating tubesextending across the entrances of said gas passes and above said commoncombustion chamber.

3. In the superheating of steam by high temperature furnace gases, amethod of controlling superheat which comprises, producing a stream offurnace gases which is of non-uniform temperature in its cross section,dividing the stream of furnace gases into a plurality of parts forwardlyof the superheater, using one of the divisions of said gases forsuperheating, independently controlling the quantity of gases suppliedto said divisions and simultaneously controlling the temperature of thegases utilized for superheating, independently controlling thefractional part of the total quantity of gases utilized for superheatingwhile using the remainder of the total quantity of gases for vaporgeneration only, and coordinating said independent controllingoperations with reference to the temperature of the superheated steam.

4. In a water tube steam boiler, a furnace, a steam and water drum,steam generatingtubes extending across the path of the furnace gases,circulatory tubes in an upright row connecting the steam space of thedrum and the steam generating tubes and extending around a side of thedrum toward the furnace gases, means connecting the generating tubeswith the water space of the drum, and hangers connected to the drum andthe circulatory tubes to suspend the latter in row formation from thedrum.

5. In a steam generating installation, a furnace, a drum at each of twoopposite positions near the opposite walls of the furnace, steamgenerating tube sections upwardly inclined from said drums toward acentral position relative to gas flow from the furnace, and uptake tubesections receiving fluid from the generating sections and outlining anupright wall separating parallel gas passes, a superheater in one of thepasses, an economizer in the other, and means for proportioning the gasflow through the passes to control superheat.

6. 'In a water tube steam boiler, a boiler setting, a boiler furnace inthe setting, a steam and water drum, fluid heat exchange tubes.delineating a wall separating two parallel gas passes leading from thefurnace, a fluid chamber communicating with said tubes at the base ofthe wall, inclined steam generating screen tubes extending from oppositesides of the chamber across the entrances to said gas passes andconnected into boiler circulation to and from the drum, an economizer inthe first of said passes, a superheater in the second pass, and means toregulate the gas flow over the superheater and thereby controlsuperheat.

7. In combination with a water tube steam boiler, a furnace, meansforming parallel gas passes leading from the furnace, oppositelyinclined steam generating tubes extending across the entrances of thegas passes, a first economizer section in one of said passes, asuperheater in the other pass, and a second economizer section exposedto furnace gases after they have passed over the superheater, saideconomizer sections being connected to the boiler and a source of feedwater supply.

8. In a water tube steam boiler; a furnace fired from opposite sideswith a slag formingfuel; a superheater; and a double slag screen; saidslag screen comprising lower banks of tubes converging downwardly intothe furnace and upper banks of tubes converging upwardly toward anintermediate position, the superheater being positioned beyond the slagscreens with reference to gas flow.

9. In a water tube steam boiler; a furnace burning a slag forming fuel;fluid heat exchange tubes contacted by the furnace gases; and a doubleconvex slag screen operating to prevent deposition of slag on saidtubes; said screen comprising upper banks of inclined tubes convergingupwardly across the path of the furnace gases from opposite sides of thefurnace, lower banks of inclined tubes converging downwardly from thesame sides of the: furnace, and means for connecting said tubes intofluid circulation.

10. In a high head water tube steam boiler, a boiler setting, a steamand water drum at the top of the setting, a furnace at the lower part ofthe setting, steam generating tubes including wall tubes depending fromsaid drum, downcomer wall tubes at opposite sides of the first mentionedwall tubes and co-operating therewith to form parallel gas passestapering upwardly, banks of superheater and economizer tubes extendingacross said passes, and means for supporting said last named tubes fromthe wall tubes.

11. In combination with a steam boiler, a furnace including a pluralityof combustion chambers, a wall including wall cooling tubes separatingsaid chambers and having extensions forming slag screens upwardlydiverging from said wall, down shot burners utilizing a slag formingfuel and directing flames against said wall from opposite directions,walls forming parallel gas passes beyond the slag screens relative togas flow, and a superheater in one of said gas passes.

12. In a water tube steam boiler, a steam and water drum, a first wallincluding uptake tubes communicating with the drum, rows of downcomersconnected with the water space of the drum and extending downwardlytherefrom to delineate walls forming upwardly tapering gas passesseparated by said first wall, means forming a fluid pressure chamberbetween said passes and having the lower ends of the uptake tubesconnected thereto, a header or drum connected to each row of downcomers,a bank of inclined steam generating tubes extending from each drum orheader to said chamber, and auxiliary fluid heat exchange tubesextending across said gas passes.

13. In a water tube steam boiler, a furnace, a boiler circulation systemincluding tubes delineating a plurality of gas passes extending inparallel from the furnace, a superheater in one pass, an economizer inthe other pass and means for proportioning the flow of furnace gasesbetween said passes to the end that superheat is controlled, said meansincluding two sets of fuel burners at opposite sides of the furnace withone of said sets positioned at the superheater side of the furnace.

14. In a water tube steam boiler, a boiler furnace, steam generatingtubes over which the furnace gases pass, means forming a plurality ofgas passes communicating with the furnace in parallel, a superheater inone of said passes, an economizer in the other pass, and meansproportioning the flow of furnace gases over the economizer and thesuperheater, saidlast named means including two sets of burners onopposite sides of the furnace with one set being on the side of thesuperheater gas pass.

15. A steam generator comprising a setting, means providing a combustionchamber, a bank of steam generating tubes disposed above said chamberbut at a substantial distance below the top of the setting, a steam andwater drum located adjacent to the top of the setting, a plurality ofcirculating tubes connecting said bank with said steam and water drum,means within the setting for providing a plurality of vertical gaspasses above said bank, said passes being arranged in parallel, meansproviding auxiliary heat absorbing surface in each of said passes, saidauxiliary heat absorbing surface including a superheater disposed in oneof said passes, an economizer disposed in another of said passes, a drumor header between said passes, and banks of steam generating tubesconnected to said drum or header and extending across the entrances tosaid gas passes.

16. In a steam boiler combination, a boiler setting, two side-by-sidehopper bottom furnaces with the inclined sides of the hopper bottoms andthe adjacent furnace walls defined by wall cooling tubes connected intothe boiler circulation, the division wall between said furnacesincluding a double row of said wall tubes communicating with a commondrum or header to compensate for tendencies to develop differentcirculation condi tions in the wall tubes of the respective furnaces,means for independently firing the furnaces, spaced tubes forming aconvection heated section subjected to the heat of the furnace gases,means forming a furnace gas chamber common to the outlets of saidfurnaces and located forwardly of said section relative to gas flow,said last named means including oppositely inclined banks of furnacescreen tubes extending across said furnace outlets and acting to receivethe fluid discharged from said division wall tubes, a steam and waterdrum above said section, and means establishing communication betweenthe discharge ends of said screen tubes and the drum, the division walltube portions acting as risers for tube portions defining parts of thehopper bottoms.

surfaces; and regulating the velocity, tempera ture, and volume of gasespassing over the economizer surfaces of each division.

18. A steam generator comprising, in combination, a plurality ofcombustion chambers, means for independently firing said combustionchambars, a gas radiation chamber receiving furnace gases from thecombustion chambers, screen tubes between each combustion chamber andthe gas radiation chamber, a pair of parallel chambers eachforming acontinuation of the gas radiation chamber and providing separate gaspasses leading therefrom, screen tubes across the entrances of saidpasses, a superheater section and an economizer section in one of thegas pass chambers, anothler econbmizer section in the other gas passchamber, a flow regulator for each of the said gas pass chambers, and asteam and water drum to which the superheater and economizer sectionsare connected.

19. A steam generator comprising, in combination, a plurality ofcombustion chambers, a partition including baille tube sections betweenadjacent combustion chambers. a gas radiation chamber leading from theoutlets of said combustion chambers, and means for directing furnacegases from the radiation chamber in two independent paths over aneconomizer section in one instance and a superheater section and anothereconomizer section in the other instance.

20. A steam generator comprising, in combination, a plurality ofseparate combustion chambers, a gas radiation chamber into which each ofthe combustion chambers open, a pair of chambers each forming anindependent continuation of the gas radiation chamber and providingseparate gas passes therefrom, wall cooling tubes lining the walls ofeach gas pass chamber, an economizer section in one gas pass chamber, asuperheater section in the other gas pass chamber, and means forcontrolling the rate of heat transfer in each gas pass chamber.

21. In' a water tube steam boiler, laterally adjacent furnaces, meansincluding downshot pulverized fuel burners for independently firing thefurnaces, a water cooled wall including wall tubes separating saidfurnaces, water tubes connected into the boiler circulation and forminga screen across the gas outlet of one of said furnaces, means forming asecondary combustion zone beyond said screen, a plurality of convectionheating gas passes arranged in parallel and leading from the secondarycombustion zone, a superheater in one of said passes, and an economizerin one of said passes.

DANA H. N. MAYO.

